A termination region is provided around an active region in order to maintain a breakdown voltage of a semiconductor power device. The termination region has a function of reducing the field strength of an end portion of the active region. Therefore, the breakdown voltage of the semiconductor power device is maintained. It is necessary to significantly reduce a termination length which is the length of the termination region in order to reduce a chip size.
A reduced surface field (RESURF) structure or a variable layer doping (VLD) structure based on an impurity layer charge balance (charge compensation) principle is used in order to reduce the length of the termination region. However, in some cases, the breakdown voltage is changed due to a charge imbalance caused by a variation in the impurity concentration of the termination region. When the breakdown voltage is changed due to the variation in the impurity concentration, there is a concern that a desired breakdown voltage will not be obtained. In addition, in some cases, the external charge is propagated to the termination region while the semiconductor power device is operating or when the semiconductor power device is in a standby state. In this case, there is a concern that a charge imbalance will occur, the breakdown voltage will be changed, and reliability the power device will be reduced. For this reason, it is necessary to prevent a variation in breakdown voltage caused by a charge imbalance.